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power wirer for the heater switch

I looked around on line and found some information about a green power wirer for the heater switch. Near as I can figure, the power of the heater switch is a green wirer that goes from the fuel gauge to the switch. I assume the wire would go over the top of big gauges and onto the fuel gauge, but I guess the wire could go along the bottom of the dash. Does this sound correct?

Re: power wirer for the heater switch

Yes, I know. That's the only one that shows the connection to A2. The factory diagrams don't show it at all, but the text in the workshop manual says to connect it to the hot side of the wiper switch, which is controlled by the ignition switch on earlier cars. On later cars, I believe it was connected to the hot terminal on the fuel gauge, which again is controlled by the ignition switch and protected by the fuse.

There are a few other minor details on that diagram that aren't right, but it's pretty close. The fellow that originally produced it did not own a TR3A, and apparently was just condensing information from the manuals. The preliminary version he sent me for review said only "Where does this connect" He sold Advance AutoWire shortly after that, IIRC he had some health issues and wanted to spend more time with his grandkids.

Re: power wirer for the heater switch

This car is TS 27036 so it is kind of early. I like the idea of the wiper switch because that switch is closer to the heater switch, but the fuel gauge already feeds that switch, so it really would not matter much. Those little tiny nuts on the fuel gauge are becoming more of challenge for me and they are probably hard to find, and the wiper switch has the lug for the wire, so that could be a plus. I need to dive in and see.

Re: power wirer for the heater switch

David & Randall got it right...Use the A4 connector at your fuse block.
That's where the green wire to the fuel gauge comes from & it's much
easier to get to. It is switched and fused which is what you want.

Re: power wirer for the heater switch

I recently went back over my wiring harness assembly and found a discrepancy with the wiper motor and hooking up the heater. Because the car is a 1958, I was using wiring diagrams from both a tr3 and tr3a that I got on line sometime back. I googled some questions I had about the wiper switch and found an old post where Randall and Geo are helping a member with his wiring diagram.

Anyways, there was a second wire green coming of the fuel gauge wiring and “hermanmaire” (the member being help) struggled where to hook this wire. I have the same second green wire about 6 inches long with a bare end on my new harness. Then it hit me this second green wirer is for the heater motor and put on at the factory.

I figured the green wire was power for the wiper motor, and black and green was the other side, but when I looked into the old post deeper I saw how Geo talked about the ground wire is used for the switch on wiper motor with no power in play on the switch and Randall wrote about how only the very early tr2s used power on the wiper switch.

So I hooked the heater to the second green wire on the fuel gauge wiring and hooked the other side of the wiper switch to ground. This should work. The other way I had it would have let smoke out for sure.

So if you have a new wiring harness with 3 wires at the fuel gauge, the extra one if for the heater. The bummer was I had the oil gauge hooked up and center dash and the heater installed. I was able to rework the wires in place through the glove box hole, but challenging.

Re: power wirer for the heater switch

What puzzles me is that in your photo, the "extra" wire appears to be green with a black stripe. Normally, GB would be the line from the fuel gauge to the fuel sender in the tank, and there shouldn't be anything else connected with it.

Re: power wirer for the heater switch

I saw that; it is a shadow. The green with black is very dark and the black strip is difficult to see, and I ran that from the switch to the wiper motor. Does it matter which post the BG goes to on the motor? I put it on the bottom post because I found pictures of the GB on the wiper motor that way.

Re: power wirer for the heater switch

Excellent wiring diagram Randall; it is the best one I have seen. Plus thanks a lot for pointing out the 1& 2 post on the wiper motor. The one is on the bottom. None of the other diagrams show that. I believe that is the one that you edited, good job. I think I have seen it before, but now I see the diagrams value. I am getting close to a smoke test; that would have been positive for smoke if I would have used my combination of tr3 and tr3a diagram I got on line.